Gardening with Laurie: Some nematodes are beneficial to your garden

By Laurie Garretson
Feb. 6, 2014 at midnight
Updated Feb. 5, 2014 at 8:06 p.m.

There are many words that conjure up bad thoughts in a gardener's mind. I find that usually when I use the word nematodes, fellow gardeners get a very disgusted look on their face.

They immediately think of destruction in their garden plots. But most of the time, I'm referring to a good thing. Yes, there are bad nematodes that no gardener would want to ever find in their gardens, but there are also very beneficial types of nematodes.

Nematodes are very tiny, wormlike creatures that naturally occur in soils all over the planet. There are as many a half a million different varieties of nematodes on the planet today. Not all these varieties are bad; in fact, most are very good.

Here are a few reasons why we want beneficial nematodes in our soils.

Beneficial nematodes are harmless to animals, plants, birds, earthworms and humans. They can easily be applied to vegetable gardens, lawns, flower beds, orchards and containers.

Wherever there is soil, they will help to control large groups of soil-inhabiting pest insects as well as above-ground pests that spend some stage of their life in the ground.

Hose-end sprayers, pump sprayers and watering cans are usually how they are applied. There is no need for any safety equipment, and they will not leave any residues, so you can even apply at harvesting time.

Nematodes need moisture in the soil to move around. Even a thin film of water on a soil particle helps them to get to their prey. It is best to water the area well before and after applying nematodes.

Beneficial nematodes are so helpful to us because they have such a large range of pest insects that they will go after. Some nematodes only rely on one specific host for their nutrients.

Hungry nematodes detect prey with their built-in honing mechanisms that tell them when there is a difference in the soil temperature and a change in the carbon dioxide levels in the soil just by following the trail of pests excrement.

Once juvenile nematodes find their victim, they enter the pest through various body openings. Once inside the host, the nematodes releases a toxic bacteria that kills the host, usually between 24 and 48 hours, and the bacteria provides nutrients for the nematodes.

As the bacteria breaks down the pest's body, the nematodes feed, mature, mate and reproduce all within the decaying body. Eventually, a single pest insect will inhabit thousands of maturing nematodes. As the host body decays, the maturing nematodes exit and search for the next pest.

Beneficial nematodes can be applied at any time of the year. If needed to control a problem with ticks, thrips and certain boars, then now is the time to apply beneficial nematodes to your soil. It is so much easier to kill pest insects with the nematodes than to battle them in their adult form.

Until next time, let's try to garden with nature, not against it, and maybe all our weeds will become wildflowers.

Laurie Garretson is a Victoria gardener and nursery owner. Send your gardening questions to or in care of the Advocate, P.O. Box 1518, Victoria, TX 77902.



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